Customizable carbon frames for bicycles or other vehicles

ABSTRACT

A lightweight vehicle frame, such as a bicycle frame, is disclosed. A first tube, which can be a cured hollow reinforced resin composite tube, is connected to a second part by a tab. The tab is tapered and is affixed to the first tube. The tab is bonded to the second part by an epoxy. The taper of the tab allows the angle at which the parts are connected to be controlled through a wide range.

This application is a divisional of U.S. application Ser. No. 11/508,080filed on Aug. 22, 2006 (now Publication No. US2007-0289136-A1 publishedon Dec. 20, 2007), which claims priority of U.S. Application Ser. No.60/710,914 filed on Aug. 24, 2005, both of which are incorporated hereinby reference.

Customized bicycle manufacturers center their philosophy on fitting andfunctionality; the better the bicycle fits the rider, the better andmore enjoyable a ride will be. Painstaking attention to detail in themanufacture of each frame is an imperative. At the inventor'smanufacturing facility, frames are handcrafted one at a time based onthe belief that excellence is a tangible quality ultimately measured byhow well the frame responds to the rider's specific needs. Every singlecustomized frame that is created is built to order, with geometry, tubediameter, tube thickness, and butting specifically chosen for therider's size, weight, and riding style. Rider information is imputedinto the bike building process as weight, flexibility, intended usage,and riding preferences. Based upon these parameters, for example,customized bike manufacturers customize the bike's tube set to enhancethe frame's ride quality.

The joints in bicycle frames greatly influence the design, construction,and performance of the frames. Joints between frame members are not onlythe most frequent source of structural problems occurring in bicycleframes; they are also limiting factors regarding one's ability tocustomize a bicycle. This is because (1) internal structural loads aregenerally the greatest at the joints; (2) it is difficult to bonddifferent materials at the joints; and (3) the joint components do notallow for any angle variability for the mating frame members. As aresult, a number of proposals have been made to eliminate or greatlyreduce the number of joints in the frames, through the greater use ofcomposite materials. See U.S. Pat. No. 5,271,784; U.S. Pat. No.3,375,024; U.S. Pat. No. 3,833,242; U.S. Pat. No. 4,493,749; U.S. Pat.Nos. 4,230,332; and 4,986,949. However, there still exists a need forjoint components to facilitate a wide range of angles for the matingcomponents of a bicycle frame.

Many modern bicycle frames make use of composite materials to reduce theweight of the frames. Composite materials have a lower density, higherspecific strength and stiffness than traditionally used bicycle framemetals. One of the most common methods of joining composite tubes toeach other employs the use of metal lugs at the joints and bonding ofthe composite tubes to the metal lugs. Traditional lugs—whether metal orcomposite—restrict the shape of the tubes to round and thus do not fullyleverage carbon's unique formability and shaping opportunities.

There are several methods that have been employed to produceall-composite bicycle frames. One such method comprises joining togethercomposite tubes by wrapping uncured composite materials around andbetween the ends and formed cuts of the pre-cut tubes to be connectedand then curing the composite materials to form a connection between thetubes. See U.S. Pat. No. 5,188,384; U.S. Pat. No. 5,106,682; U.S. Pat.No. 5,019,312; U.S. Pat. No. 5,116,071; and U.S. Pat. No. 4,900,048. Theresultant frame is solid at the joints.

Another method for forming an all composite jointed frame makes use oflugs formed of composite materials using a bladder. In this method,disclosed in U.S. Pat. No. 5,624,519, bicycle lugs are formed byinserting pre-forms of stacked resin-impregnated carbon fiber plies intorespective halves of female tooling. A bladder is then placed over oneof the pre-forms and the mold is closed. The bladder is then inflated topress the pre-forms against the tooling, and the mold heated to cure theresin to form the final cured lug. The pre-forms are sized so that eachforms one half of the lug plus an overlapping portion that forms a lapedge. Accordingly, lugs manufactured by this process have dividing linesof overlapping cured composites. These dividing lines provide areas ofweakness in the lugs and undesirable increased weight.

It is an object of this invention to provide an all composite frame thathas low frame weight and high frame strength.

It is another object of this invention to provide a generally hollowbicycle frame, and processes for its manufacture. The frame is light inweight, stiff, and strong, and has a construction that is amenable tocustomization.

It is another object of this invention to provide all composite tube andtab components that are individually formed prior to assembly to havecomplementary opposing surfaces for coupling. Upon coupling, by adhesivebonding for example, a generally hollow frame is formed, having jointsof a smooth exterior surface. The tabs provide for a uniform forcetransmission across each joint. The tabs may be internal and not visibleon the exterior of the frame. Once the parts are assembled, as describedbelow, the result is a frame that provides the appearance of a moldedcarbon frame, or monocoque frame.

It is another object of this invention to provide for a completelycustomizable bicycle frame based upon facilitating a wide range of tubejoint angles at each joint within the bicycle frame; thereby allowingfor greater customization of angles and lengths, and eliminatinggeometry constraints.

It is another object of this invention to provide a frame stiff enoughand light enough for instant acceleration yet vertically compliantenough to smooth out unforgiving terrain.

SUMMARY OF THE INVENTION

Many bicycle, scooter, wheelchair and other vehicle frames aremanufactured using parts that are molded together to form a completeframe. This invention is concerned with all composite vehicle frames, inparticular a bicycle frame, made of joined parts comprising carbonfibers impregnated with resin, for example. An exemplary bicycle frameof the present invention can be formed by joining composite tubes andtabs, wherein the frame tabs are located at the joints of the frametubes and serve as connecting members between the various frame tubes50. Once the parts are assembled, as described below, the result is aframe that provides the appearance of a molded carbon frame, ormonocoque frame. This frame is completely customizable; any shape andsize of tube, and any angle between tubes, can be provided withoutlimiting customization. In a preferred embodiment, rider information isimputed into the bike building process as weight of the rider, height ofthe rider, flexibility, intended usage, and riding preferences. Basedupon these parameters, for example, custom bike manufacturers customizethe bike's tube set to enhance the frame's ride quality. The methods ofthe present invention are easily applied to manufacturing scooters,wheelchairs, carriages, cycles, bicycles and similar vehicles.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a bicycle frame manufactured using a method of the presentinvention.

FIG. 2 is a fragmentary detail view of a top tube bonded to an upperanchor via a hollow tab molded onto the upper anchor.

FIG. 3 is a side elevational view of a top tube of the invention havinga through hole oriented perpendicularly to the axis of the top tube.

FIG. 4 is a top plan view of the top tube shown in FIG. 3.

FIG. 5 is a fragmentary cross-sectional view taken substantially in theplane of line 5-5 in FIG. 4.

FIG. 6 is a fragmentary cross-sectional view taken substantially in theplane of line 6-6 in FIG. 2.

DETAILED DESCRIPTION OF THE INVENTION

This invention is concerned with an all composite vehicle frame, and inparticular a bicycle frame made of joined parts comprising carbon fibersimpregnated with resin, for example. Once the parts are assembled, theresulting frame provides the appearance of a molded carbon frame, ormonocoque frame. This frame is completely customizable; any shape andsize of tube, and any angle between tubes, can be used in themanufacturing process without limiting customization. In a preferredembodiment, rider information is imputed into the bike building processas weight of the rider, height of the rider, flexibility, intendedusage, and riding preferences, among other factors. Based upon theseparameters, for example, customized bike manufacturers customize thebike's tube set to enhance the frame's ride quality.

Segments of the customized frame of the present invention are joinedusing tabs 50 imbedded into or molded as part of an anchor. Each tab isintegrated into the anchor and formed (e.g., molded) as a hollowelement. As illustrated in FIG. 2, the tabs 50 can be shaped similarlyto tomb stones or tongues. They have an external shape 25 that closelymatches the mating tube's or part's inside shape so that the bonding gapis easily maintained. Additionally, the tabs are provided with acurvilinear taper on the distal top 5 and the sides 10 in order tofacilitate an extremely wide range of tube joint angles. The amenabilityof the corresponding joints having these tabs allow for completecustomization because the overlying tube 40 can fit over the tab 50 inany of a wide range of angles.

The tabs 50 are generally rectilinear in cross-sectional shape, and thushave flat sides 25 (FIG. 6). The tabs 50 are coated with a bonding agentas described below, to allow for adequate bonding coverage between thetab and mating tube while simultaneously providing for full angleadjustability. In addition, the rectilinear cross-sectional shape andflat sides provide a safety mechanism by facilitating alignment of themating parts, and by preventing the mating part from rotating if it wereto fully delaminate from the tab.

Each tab has an additional feature which is a groove 27 (FIG. 2) ortrough, that extends around the circumference of the tab at its base.This “catch” groove fills with a bonding agent during assembly andserves as a failsafe to prohibit the part from separating once thebonding agent dries. Once the bonding agent has filled the groove andcured, it creates a mated groove interface that makes it extremelydifficult for the bonding agent and the parts to separate.

Each anchor with its molded tab(s) is essentially ready for finalassembly when it comes out of the mold after the proper preparation andclean up that any carbon part would require, as understood by someoneskilled in the art. The mating tubes require two steps of machining.First, each tube is coped (cut or mitered) to a length, and at an angle(at its axial end(s)), for whatever frame geometry is required. This canbe of any length or angle; the tube and the entire frame are fullycustomizable. The tube is then deburred; any sharp edges or flashing areremoved. The tube is then set in a fixture that holds it in line withthe desired axis orientation required by the frame design. A router isthen employed at the coped end of the tube, axially and on the insidediameter. The router cuts to the shape of the tab plus roughly 0.010inches, to account for a gap for the bonding agent. This routing ensuresthat the part will fit adequately and maintain the correct bonding agentgap.

Once the tube is machined, the area of machining inside the tube isthoroughly coated with a bonding agent, as is the exterior of the tab onthe anchor, and the anchor and tube are joined together by telescopingthe tube over the tab and locating the tube in the desired position withrespect to the tab and adjacent frame parts.

The bonding agent used here can be of any known and suitable type. Onesuch bonding agent is Hyson 9460, a two-part epoxy available fromLoctite Corporation, 1001 Trout Brook Crossing, Rock Hill, Conn.06067-3910.

To permanently join the subassembly tubes, the subassembly is puttogether as described here. Any excess bonding agent is wiped away. Thenthe subassembly is put in an oven at approximately 250 degreesFahrenheit for approximately 60 minutes; depending on the bonding agentused. Once removed, the subassembly is complete. This process isrepeated to join all segments of a frame. All part joints can be curedsimultaneously, or in stages. Depending on the bonding agent, re-curingthe subassemblies does not typically damage the parts.

The ideal bonding conditions will vary depending on the agent used.Common parameters include a temperature range of 60-80 degreesFahrenheit, ambient atmosphere, 40-50% humidity, ambient pressure, fullcure time of 8 hours at room temperature followed by 60 minutes at 250degrees or 3 days at 77 degrees.

The foregoing description is easily applied to the manufacture ofscooters, wheelchairs, carriages, cycles, bicycles and similar vehicles.

The illustrated frame, which represents one embodiment of the presentinvention, consists of about nine molded parts. These elements may bemade of carbon fiber impregnated with resin or other suitable material.Other parts, if made of metal, can be fabricated through casting,forging, and/or machining.

The upper anchor 35 is shown in FIG. 2. It is fabricated with two tabs50 imbedded therein or molded as part thereof. Each of the tabs 50engages and is ultimately bonded to one of two mating parts, a top tube40 and a seat stay 85 (FIG. 1).

Once the top tube is machined, the area of machining is coated with abonding agent along with the exterior of the corresponding tab on theupper anchor. The top tube and the upper anchor are then joinedtogether. Any excess epoxy is wiped clean and then the subassembly iscured as described above. Once removed, the subassembly is complete.

Seat tube extensions 45, 60 and/or anchor extensions 56 are configuredso that any seat tube length can be used while simultaneouslyintegrating with the seat tube extension and anchor extension in a waythat makes this integrated framework appear to be a single seamlesspart. The parts appear to be one molded piece, but the frame size andshape is completely customizable. These extensions 45,56,60 are from thesame mold and are simply cut to length for whatever size bicycle frameis desired. The bottom of one part mates to the top of the next part orvice versa. Alternatively, both ends of some parts can make up thebottom or top of other parts.

The bottom bracket anchor 55 also includes two tabs that are integratedin the molding process. These two tabs are secured to the mating parts,a down tube 75 and a chain stay element 80.

The head tube 70 can be created from a variety of material andfabrication methods, such as machining, extruding, filament, winding orany other method known to someone skilled in the art that will yield atube of the desired shape. The head tube 70 can have a round, oval,pear, or a teardrop cross-sectional shape. The elongation of a teardropshaped tube can either be constant or it can vary over the length of thetube, depending on the tube usage. The materials from which the headtube 70 is made can be, but are not limited to, aluminum, carbon, andtitanium or any other material suitable for use in manufacturing bicycleframes. Metal head tubes are often employed in carbon framemanufacturing because of the tube's interface with the metal head set.The headset can easily damage a carbon surface so, if a frame builderuses a carbon head tube, the builder will also apply metal insert forthe headset. An entire metal head tube can actually be lighter and moreeffective than a hybrid of carbon and metal. Additionally the metal headtube has little to no impact on the ride characteristic of the frame. Itis preferable that carbon—with metal inserts—or titanium be used in themanufacturing of the head tube. At or near its upper end, the head tube70 will pass through and be bonded into the through hole opening in thetop tube 40. At or near its lower end, the head tube 70 will passthrough and be bonded into the through hole opening in the down tube 75.The head tube will accept the fork steerer.

The top tube 40 is fabricated using the same method as the upper anchor35. The top tube 40 is a hollow molded carbon fiber part. The front endof this tube is molded in such as way that it is closed by theillustrated “eye” structure 105. FIG. 5 (it is a hollow tube that isopen only on one end, the rear). A through hole 100 has an axisextending perpendicularly to the axis of the top tube part. The holeprovides an undersized starter hole for the machining step ofcustomizing and sizing the through hole to allow the head tube 70 topass through at a specified and customized angle. Once the through holeis machined, it is deburred, i.e. all flashing and sharp edges areremoved and it undergoes secondary filing so that the parts fit togetherwith little to no gap. Next the surface that will be bonded is prepared.This typically consists of roughing up the surface through sandblasting, rough machining, hand sanding, or a similar method. Then thepart is degreased with acetone or similar cleaning agent or solvent. Itis affixed by a bonding agent to the head tube 70. The rear end 110 ofthe top tube 40 is joined to the upper anchor 35 as described above; thetop tube and the upper anchor are bonded together. This unique designwith its epoxy groove is a failsafe arrangement so that the parts cannotcatastrophically separate.

The down tube 75 is fabricated, machined, and bonded in much the sameprocess as for the top tube 40. In accordance with the invention, thedown tube 75 is can have any cross-sectional shape desired. As suggestedhere, the tubes are multishaped over their lengths. The front end ofthis tube is molded in such as way that it is closed (it is a hollowtube that is open only on one end). The front end of the down tube hasan opening (the “eye”) and looks like a needle. The through hole has anaxis which is oriented perpendicularly to the axis of the down tubepart. The hole provides an undersized starter hole for the machiningstep of customizing and sizing the through hole to allow the head tube70 to pass through at a specified and customized angle.

The chain stays element 80 is hollow and looks somewhat like a tuningfork. It connects to the bottom bracket anchor 55 in the same way as thetop tube 40 connects to the upper anchor 35.

The seat stay element 85 is also hollow. It has a router-made cutout tomate with the tongue of the upper anchor 35.

Dropouts 90 are standard on all bicycles. The dropouts are either metalor carbon—typically metal—and serve the purpose of holding the wheelaxle and rear derailleur safely and perpendicularly to the bicycleframe.

For each bicycle, there is a saddle holding mechanism 60,45. Thisillustrated mechanism allows the seat tube to extend into the saddle;therefore, a customary seat post is not needed. The seat tube has anaerodynamic shape. The saddle holding mechanism system is not arequirement for this type of joining methodology. It is an option. Theseat tube could be round, oval, pear, or tear drop shaped. The saddleholding mechanism could optionally be a traditional seat post.

There are other known components necessary to be incorporated onto theframe to manufacture a complete bicycle. These components include forks,stems, seat posts, crank sets, and wheels of known design.

Although a preferred embodiment of the bicycle frame and method ofmaking a bicycle frame has been disclosed, it is to be understood thatthe present disclosure is made by way of example; and that variationsare possible without departing from the subject matter coming within thescope of the following claims.

1. A customized vehicle frame comprising at least a first cured hollowreinforced resin composite tube and at least one other frame part havingat least one tab which is secured to the at least first tube, whereinthe at least one tab has sides which are substantially flat over atleast a portion thereof, and a curvilinear taper defining the tab top,wherein the tab top is tapered away from the part having said tab over amajority of the length of said tab, thereby allowing the attachmentangle of the tube, in relation to the part having the tab, to becustomized and adjusted.
 2. A frame according to claim 1, wherein thepart having the tab is a second cured hollow reinforced resin compositetube.
 3. A frame according to claim 2, wherein the first and the secondtubes are sized according to rider information.
 4. A frame according toclaim 3, wherein the rider information is selected from the groupconsisting of rider weight, rider height, flexibility, and intendedusage.
 5. A frame according to claim 4, wherein the vehicle is selectedfrom the group consisting of a wheelchair, scooter, and bicycle.
 6. Aframe according to claim 5, wherein the vehicle is a bicycle.
 7. A frameaccording to claim 2 wherein at least one of said first or second tubeshas a non-circular cross-sectional shape.
 8. A frame according to claim1, further including a bonding agent bonding the tab to the tube.
 9. Aframe according to claim 8, wherein the bonding agent includes epoxymaterial.
 10. A frame according to claim 1, wherein the tab defines agroove for receiving a bonding agent.
 11. A frame according to claim 1wherein the finished frame has the appearance of a molded monocoquecarbon frame.